Over the past 15 years the co-investigators and their colleagues have developed the Health Belief Model, a theory to explain preventive health behavior and behavior taken in response to illness which will be used to study adherence behavior of all identified hypertensives in Tecumseh, Michigan. This community of about 11,000, which has been under continual study by the School of Public Health since 1959, affords the unique opportunity to study adherence behavior at all levels in a total population, including 1) persons screened through 1969 who did not visit their physician for definitive diagnosis, 2) those who made a single visit but did not follow-up, 3) those who began to comply with treatment but who stopped early, 4) those who continued treatment for an extended period before becoming non-adherents, and 5) those who have continued to comply with recommended medical regimens. All patients are under private physician's care. In addition, a group of hypertensive patients of private practitioners in Washtenaw County will be interviewed to test further the applicability of the Health Belief Model and other factors to adherence. A series of educational interventions will be undertaken in Tecumseh including a variety of written messages, reinforcements through reminders by a nurse, self-monitoring, including patient's taking of their own blood pressures and use of the patient's social support system.